Differences in the microcirculatory effects of local skin surface contact pressure stimulation between acupoints and nonacupoints: possible relevance to acupressure

In the present study, laser Doppler measurement was used to quantitatively investigate the microcirculatory effects of contact pressure stimulation (PS) underneath the Hoku acupoint and its nearby nonacupoint, to improve the understanding of the mechanisms underlying acupressure therapy. A control group (no PS applied) and three experimental groups with different applied PS (group A, 60 mmHg on the Hoku acupoint; group B, 60 mmHg on a nearby nonacupoint; group C, 50 mmHg on a nearby nonacupoint) were studied. Each experiment involved recording data of a 20 min baseline and two periods of effects after stopping PS. The relative energy contribution (REC) in five frequency bands, as revealed by Morlet wavelet transformation, was calculated. At the pressed site, the average value of the laser Doppler flux signal was increased only in group A, and coefficient of variance of the amplitude sequence was only significantly decreased during measurement (M1: 0 to 20 min) in group B. The RECs of the myogenic-related band were significantly increased in groups A and C, whereas there were no significant changes found in group B. The improved microcirculatory blood-flow perfusion at Hoku may partly explain why acupressure can exert better therapeutic effects than PS applied to other sites. The laser Doppler spectra responses illustrated that the induced pressure-induced vasodilation can be attributed mainly to the myogenic response. Laser Doppler measurement and analysis therefore represent a noninvasive method of examining the microcirculatory efficacy of acupressure therapy.